curing questions

[PizzaJNKY]

I've completed 2 days worth of fire curing, and the interior of my dome has turned black, but has not yet turned white.

Does a certain temperature have to be reached for dome to turn white?

I also have not yet wrapped the dome with FB blanket. My plan was to apply the blanket then cover with perlite/mortar after the cure.

Should I apply the blanket and perlite/mortar now, or is it okay to wait till curing process is over?

[dmun]

Re: curing questions

There is some disagreement about this. I think the consensus is that it's better to apply the blanket and the perlite concrete before the curing fires, because the dome heats more uniformly as you get toward the cooking temperatures. A hot fire on the inside, and cooling breezes on the outside sets up thermal expansion forces that may lead to excessive cracking.

Also, there's a lot of water in the vermiculite concrete that needs to be driven off.

[gjbingham]

Re: curing questions

Agreed! We keep talking about these things. The questions keep coming up. How can we make this more obvious so that other members don't go down the wrong path?

[dvonk]

Re: curing questions

Yes, your bricks will become white when it will be hot enough for carbon to burn out from the surface, but not to condense (as bricks are cool at the beginning).
It doesn't matter how many days did you firing - if you don't reach the point, it will stay black.
And it will turn black at each firing beginning.

[thebadger]

Re: curing questions

I thought the you just put the blanet over so you could keep the heat in and then take it off to check for cracks...

I'm almost where PizzaJNKy is in that once I finish my vent/landing I'm ready to cure...

So I should blanket and coat first, then wait 1-2 weeks then cure???

We have so much information on the site that it's hard to find it (is there a "how to search" thred). It would be great to have an FAQ page or a location where the "approved" answers are located from James and the "senior builders" out there.

I'm still fuzzy on the "approved" curing method...

Thanks
Dick

[Frances]

Re: curing questions

One of the really cool things about this site is that everyone has built a slightly different oven, so what may be valid for one oven may not be for another... and in some cases there doesn't seem to be a wrong or a right, but merely several different opinions, or a consensus that can can change over time....

That said, the new improved and currently most popular curing method is here:

http://www.fornobravo.com/forum/f16/curing-strategy-3227.html

And I think it really needs to be made into a sticky!!!

As for curing before or after insulating, as dmun says its probably better to insulate first... unless you have some good reason not to: I cured first, because the insulation I rustled up doesn't react kindly to getting damp... so I needed to drive off the water in the dome beforehand.

And... no cracks But I used a different kind of mortar, so that proves nothing. See what I mean?

[PizzaJNKY]

Re: curing questions

Today, I applied the FB blanket. It went on easy, and stays in place. I am not going to apply the Perlite/mortar insulation layer till after the curing process. I like the idea of being able to check for cracks after the cure. Now that I have put the insulation blanket on, I noticed that the oven gets hot a lot sooner. It is currently at 600 degrees, and I am using same amount of wood that it took to get up to 300 without the insulation.

[james]

Re: curing questions

It is currently at 600 degrees, and I am using same amount of wood that it took to get up to 300 without the insulation.

High tech insulation is pretty remarkable stuff. I had the exact same experience a few months ago. You keep telling yourself how important the insulation is -- and it's still cool to see it first hand.

My take on the question of whether to cure with, or without, the insulation layer depends on a couple of things. For FB pre-made ovens, it is safe and recommended to complete the installation with all of the insulation before you cure. There really isn't a risk of cracks. That said, make sure your vent area is fully airtight before you finalize your enclosure.

If you think your dome is totally solid, go ahead and finish your insulation before you start curing. I think you will do a better job of keeping the heat of the oven at the right temperature (the insulation will help hold the oven at the constant 300?F you are looking for), and if you are using vermiculite concrete, the curing has to also cure the moisture out of that layer.

If you think your dome definitely needs a sanity check before you move on to the next steps, you can cure without insulation -- but, I still think it would be better to wrap the oven with one blanket, and be prepared to pull it back to make sure the oven isn't leaking.

What do everybody think?

James

[PizzaJNKY]

Re: curing questions

James, If I do find that the oven has some cracks or is leaking in certain spots after the cure, do I need to apply more Refmix to patch the cracks, or will perlite/portland or perlite/regular mortar work? The reason I ask, is that I am out of Refmix.

[Ken524]

Re: curing questions

My curing went smoothly with the blankets installed. I didn't bother taking them off to peek afterwards. I had some hairline cracks on the interior and didn't really care what the exterior looked like. My vote is to throw the blankets on, start curing and proceed to next step of finishing the oven.

[PizzaJNKY]

Re: curing questions

Thanks Ken. I like your vote. Even though I've enjoyed my build, I'm getting tired, I want to be done, and I just want to eat...Soon!

I was thinking even if there are cracks, the blanket and the perlite/mortar cover should keep them in check anyway.

[Ken524]

Re: curing questions

I was thinking even if there are cracks, the blanket and the perlite/mortar cover should keep them in check anyway.

I agree... Because of the way the bricks are positioned, I doubt you'll ever have a brick fall or come loose in the dome (arch is a different story ). Several layers of blanket and vermiculite over the cracks will keep the heat and smoke where it belongs.

[PizzaJNKY]

Re: curing questions

Man that FB blanket is amazing! Yesterday, during the cure, the oven never got hotter than 600, and it was 450-550 most of the day. I stopped putting in more logs at about 3:30 pm. At the end of the cure, I placed bricks infront of the entryway, since I don't have a door yet. I just checked the interior temperature, and it is at 266.